The present invention relates to an automobile disk brake of the guide pin type.
An automobile disk brake of the guide pin type is shown in FIG. 3. In this disk brake, a pair of pins 18 and 19 are screw-engaged in tapped holes 20 and 21 to attach a caliper-shaped member 6 to a support 1 so that the caliper-shaped member can be optionally displaced relative to a support. The tapped holes 20 and 21 are provided in the support 1 at both ends thereof. The threaded shank portions 18a and 19a of the pins 18 and 19 are tightened in the tapped holes 20 and 21, respectively, to secure the pins to both the end portions of the support 1. Cylindrical guides 23 are provided to both ends of the caliper-shaped member 6, and are fitted by means of sleeves 22 on the pins 18 and 19, or directly fitted on the pins, to attach the caliper-shaped member to the support 1 so that the caliper-shaped member can be optionally displaced relative to the support.
However, since the pin 18 and the sleeve 22, which support the caliper-shaped member 6 to make it optionally displaceable relative to the support 1, and the cylindrical guides 23, which are provided in the caliper-shaped member, are slidably fitted with each other, it is inevitable that very small gaps will develop between the outside circumferential surface of the sleeve 22 and the inside circumferential surface of the cylindrical guide 23 and between the outside circumferential surface of the pin 18 and the inside circumferential surface of the other cylindrical guide 23. Because of the presence of those gaps, the axes of the pins 18 and 19 and those of the cylindrical guides 23 become skewed with respect to one another if the contact portions 29 of the caliper-shaped member 6 and a backing element of a friction pad are offset to each other along the axial directions of the cylindrical guides 23 or if the center of gravity of the caliper-shaped member 6 is not located between planes perpendicular to the pins 18 and 19 and extending on the ends of the pins. In that case, the cylindrical guides 23 of the caliper-shaped member 6 deviate relative to the pins 18 and 19 parallel with the axis of gyration of a rotor 9, so that the cylindrical guides 23 become skewed with respect to the axis of gyration of the rotor. As a result, the directions of forces which push a pair of friction shoes 10 on the inside and outside 9a and 9b of the rotor 9 become unparallel with respect to the axis of gyration of the rotor. For that reason, the directions of the forces which push the linings of the friction pads 10 on the inside and outside 9a and 9b of the rotor 9 become unperpendicular to the inside and outside of the rotor, so that the forces which act on the radially inner and outer portions of the linings of the pads 10 become uneven. As a result, the linings are not uniformly worn. When the linings are nonuniformly worn, a noise is made in braking or the braking power of the disk brake diminishes.